The Saffir-Simpson hurricane scale is a 1-5 rating based on the hurricane's present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf and the shape of the coastline, in the landfall region.
- Category 1 Hurricane: Winds from 74 to 95 mph. No significant damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some damage to poorly constructed signs. Also, some coastal road flooding and minor pier damage.
- Category 2 Hurricane: Winds from 96 to 110 mph. Some roofing material, door, and window damage of buildings. Considerable damage to shrubbery and trees with some trees blown down. Considerable damage to mobile homes, poorly constructed signs, and piers. Coastal and low-lying escape routes flood 2 to 4 hours before arrival of the hurricane center. Small craft in unprotected anchorages break moorings.
- Category 3 Hurricane: Winds from 111 to 130 mph. Some structural damage to small residences and utility buildings with a minor amount of curtain wall failures. Damage to shrubbery and trees with foliage blown off trees and large trees blown down. Mobile homes and poorly constructed signs are destroyed. Low-lying escape routes are cut by rising water 3 to 5 hours before arrival of the center of the hurricane. Flooding near the coast destroys smaller structures with larger structures damaged by battering from floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles or more. Evacuation of low-lying residences with several blocks of the shoreline may be required.
- Category 4 Hurricane: Winds from 131 to 155 mph. More extensive curtain wall failures with some complete roof structure failures on small residences. Shrubs, trees, and all signs are blown down. Complete destruction of mobile homes. Extensive damage to doors and windows. Low-lying escape routes may be cut by rising water 3 to 5 hours before arrival of the center of the hurricane. Major damage to lower floors of structures near the shore. Terrain lower than 10 ft above sea level may be flooded requiring massive evacuation of residential areas as far inland as 6 miles.
- Category 5 Hurricane: Winds greater than 155 mph. Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. All shrubs, trees, and signs blown down. Complete destruction of mobile homes. Severe and extensive window and door damage. Low-lying escape routes are cut by rising water 3 to 5 hours before arrival of the center of the hurricane. Major damage to lower floors of all structures located less than 15 ft above sea level and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5 to 10 miles of the shoreline may be required
The terms used to describe the progressive levels of organized disturbed weather in the tropics that are of less than hurricane status are:
- Tropical Disturbance: A discrete tropical weather system of apparently organized convection, 200 to 600 km (100 to 300 nmi) in diameter, originating in the tropics or subtropics, having a nonfrontal migratory character, and maintaining its identity for 24 hours or more.
- Tropical Depression: A tropical cyclone with a closed circulation in which the maximum sustained wind speed 38 mph.
- Tropical Storm: A tropical cyclone in which the maximum sustained surface wind speed from 39 to 73 mph. The convection in tropical storms is usually more concentrated near the center with outer rainfall organizing into distinct bands
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